Jet Dyeing

Jet dye machines resemble becks in that the fabric is sewn into a continuous loop which is circulated through the machine. However, the cloth transport mechanism is dramatically different in these two types of machines. A high speed jet of dye liquid created by a venturi transports the fabric through the cloth guide tube of the jet machine. A jet machine has a cloth guide tube for each loop of fabric being processed. A powerful pump circulates the liquor through a heat exchanger outside of the main vessel and back into the jet machine. The fabric travels at high velocity of 200-800 meters per minute
while it is in the cloth guide tube. The fabric leaving the cloth guide tube enters a larger capacity cloth chamber and gradually advances back toward the cloth guide tube.

Jet dye machines are usually pressurized to provide for high temperature
dyeing capability. High temperature jet dye machines are especially suitable for delicate fabrics made of texturized polyester. The jet principle is also used in atmospheric machines designed for dyeing temperatures up to 100°C.

Jet dye machines provide the following advantages compared to
atmospheric becks for dyeing fabrics made from texturized polyester.

1. Vigorous agitation of fabric and dye formulation in the cloth tube increases the dyeing rate and uniformity.

2. Rapid circulation of fabric through the machine minimizes creasing because the fabric is not held in any one configuration for very long at a time.

3. Lengthwise tension on the fabric is low so the fabric develops bulk and fullness of handle.

4. Dyeing at high temperature of about 130°C gives rapid dyeing, improved dye utilization, improved fastness properties, and makes possible the elimination of carriers which are required when dyeing at lower temperatures.

5. The lower liquor ratio used in jet dyeing allows shorter dye cycles and saves chemicals and energy.

Some disadvantages of jet dye machines compared to becks are as follows:

1. Capital and maintenance costs are higher.

2. Limited accessibility makes cleaning between dyeings and sampling for color during the dye cycle difficult.

3. The jet action tends to make formulations foam in partially flooded jet machines.

4. The jet action may damage the surface of certain types of fabrics. Jet dyeing machinery evolved steadily after invention of the machine in 1961. The first machines were partially flooded. Fully flooded machines keep the fabric completely submerged during the dye cycle. This prevents the formation of longitudinal creases which occur when the fabric is lifted from the bath in a partially flooded machine. Fully flooding the machine also prevents formation of foam.

The so-called "soft flow" machines use the same principle of a trans port tube as a jet machine where the fabric is transported in a stream of dye liquor. However, transport of the fabric in soft flow jet machines is assisted by a driven lifter reel. These machines either eliminate the high velocity jet or use a jet having lower velocity than that used on conventional jet dying machines. The soft flow machines are more gentle on the fabric than conventional jet machines. Jet machine offering capability of very low liquor ratios .

Dye Process

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